It was a bad week for Aaron Chesley. He talked back to the staff at a Baltimore homeless shelter, got into an argument with a fellow veteran and missed an appointment for his post-traumatic stress disorder counseling session.

"Are you still watching the news?" his counselor, Anthony Holmes, asked.

Maybe that's what had set Chesley off. He had been showing progress since he came to the program last fall. But television footage from the war could cast him back in Iraq in an instant, back to fingering the trigger of his machine gun, scanning the horizon for insurgents. And Holmes knew it wouldn't take much for Chesley to land back on the streets.

"No. If the news is on, I turn my back," Chesley said.

In a homeless shelter filled with Vietnam War veterans, Chesley, 26, a former Catonsville High School honors student who joined the West Virginia Army National Guard in 2000 to help pay for college, was the only one in the facility who fought in the country's latest conflict. But across the nation, veterans of recent combat in Iraq and Afghanistan are slowly starting to trickle into shelters, officials say.

The number of homeless veterans from recent wars is hard to gauge. From 2004 to 2006, the Department of Veterans Affairs provided shelter to 300 veterans of Iraq and Afghanistan tours, out of the tens of thousands who have served.

That figure "is not even close to accurate," said Paul Rieckhoff, executive director of the Iraq and Afghanistan Veterans of America, because it doesn't include the "others sleeping in buses, their cars or on the streets."

In New York City alone, he said his organization has helped 60 homeless veterans since 2004.

As in the Vietnam War era, when thousands of vets ended up homeless, there are already signs that the recent conflicts are taking a traumatic psychological toll on some service members. Many veterans' advocates said that despite unprecedented attempts by the military and Veterans Affairs to care for veterans, increasing numbers of the new generation of warriors are ending up homeless.

"This is something we need to be concerned about," said Cheryl Beversdorf, president of the National Coalition for Homeless Veterans, a Washington-based nonprofit.

Not everyone agrees, however, that the wars will spark a significant uptick in homelessness. Peter H. Dougherty, director of Veteran Affairs' Homeless Veterans programs, said that the administration is "light years ahead" of where it was during the Vietnam era. Without a draft, today's all-voluntary military is "better physically and mentally prepared" for combat, he said. The department now also provides free health care for two years after Iraq and Afghanistan vets get out of the military, and it's focusing on preventive services that help veterans and their families cope.

"We are continuing to expand services, but we don't see any influx yet," he said.

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The debate comes as Army studies have found that up to 30 percent of soldiers coming home from Iraq have suffered from depression, anxiety or PTSD. A recent study found that those who have served multiple tours are 50 percent more likely to suffer from acute combat stress.

Veterans' homeless shelters across the country, such as the Maryland Center for Veterans Education and Training in Baltimore, are bracing for increased demand. "The wave has not hit yet, but it will," said retired Army Col. Charles Williams, MCVET's executive director.

Nearby, the South Baltimore Station shelter is doubling the size of its program in anticipation of the Iraq war vets it expects to serve, said Woody Curry, the center's program director. He thinks it will be several years before they start showing up in large numbers.

"Usually it takes a period of time before it surfaces -- the PTSD," he said. "And the military mentality leads you to try to tough it out and not say anything."

He said he was particularly worried about members of the National Guard and Reserves who return to their civilian lives after their service. "A lot of these guys were just everyday working people, and then you put them in a situation like that," he said. In Iraq, "you're on a hyper-vigilant state all the time. You can't turn that off. It becomes who you are."

Meanwhile, a report by the Democratic staff of the House Veterans Affairs Committee found that from October 2005 to June 2006, the number of Iraq and Afghanistan veterans seeking services from walk-in veterans centers doubled, from 4,467 to 9,103.

"It's clear from the report that Vet Center capacity has not kept pace with demand for services, and the administration has failed to properly plan and prepare for the mental health needs of returning veterans and their families," U.S. Rep. Michael H. Michaud (D-Maine), a member of the committee, said in a statement.

But Dougherty said the increase shows that more veterans were receiving treatment, and that the department's efforts to reach out them has succeeded. It has started sending letters to vets returning from Iraq and Afghanistan with the location of the nearest veterans center and "encouraging them to go," he said.

"One of the big differences now is we're much more in a preventative health-care mode than we were in the past," he said. "We're hoping by getting that early intervention we'll be able to take care of them.''

Although many vets suffer from PTSD, "epidemiologic studies do not suggest that there is a causal connection between military service, service in Vietnam, or exposure to combat and homelessness among veterans," according to the Veteran Affairs Web site. Rather, homelessness in veterans is cause by an amalgam of forces: family support, finances, education, mental illness -- the same factors that cause homelessness in the general population.

The veterans department is going to considerable lengths to reach out to Iraq and Afghanistan veterans and their families, Dougherty said. There are also specialized services for women, who are an increasing part of the military force and are seeing combat in Iraq. Meanwhile, the total number of homeless veterans has gone down from about 250,000 10 years ago to about 194,000 this year.

The Army has increased the number of mental health professionals in Iraq and Afghanistan, and a pilot program where primary care physicians at Army bases screen patients for PTSD and other disorders is expanding. The military has also started following up on service members three to six months after they return from war to check on their overall physical and mental health.

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In Iraq, Chesley's unit provided convoy security, which meant the Army specialist was out on the roads exposed, always wondering when the next roadside bomb would explode.

He became hardened, he said, prepared to die: "It was kind of like you embrace death to stay alive. If you were going to die, you were going to die."

When he got home in March 2005, he struggled to adapt from the first day. He was excited to be home, and he knew his family was waiting, but as he got off the plane he felt dizzy.

Once gregarious and engaging, Chesley was withdrawn and sullen. This was not the young man who was a star athlete and an honors student, whose walls were adorned with plaques and certificates, whose principal, Robert Tomback, recently remembered him as "bright, quite charming and enormously popular."

Chesley started drinking heavily, he said, "putting coffee in my vodka just to get going in the morning." Drinking led to drugs and that led to trouble.

He stole about $600 from his mother. He was arrested twice for DUI, once after he hit a police car, the other after he flipped the truck with the windows he tinted so no one could see him drinking and smoking pot as he drove. He ended up floating between family members' homes.

He tried to resume his studies at West Virginia University, but he couldn't regain his old life.

Finally, his stepfather brought him to a VA Hospital in Baltimore, and Chesley was diagnosed with PTSD and bipolar disorder. Later, he enrolled in MCVET, the nonprofit shelter that provides drug and alcohol counseling and other services.

Sitting across from Holmes at the counseling session, Chesley was a model of contrition and promise. He vowed to take his medicine, to talk to someone if he felt rage creeping up, to "work on being respectful even if I'm angry."

Holmes finally let him go but worried.

"He's still got a lot of anger from the war," Holmes said after Chesley left. "He's on thin ice. He's on real thin ice."

A few weeks later, Chesley left the program, and its director of student services said he didn't know what happened to him.

Chesley's stepfather, Bennie Price, said he recently enrolled in a veterans program in West Virginia after "hitting rock bottom again."

Reached by phone last night, Chesley admitted he had slipped. "But I know I need help," he vowed. "And I want to succeed."